3, 7, 7-trialkyl-5-heptenol and its preparation



United States Patent "ice 3,394,169 3,7,7-Ti2lALKYL-5-HEPTENOL AND ITSPREPARATION Herman E. Davis, Kingsport, Tenn., assignor to Eastman KodakCompany, Rochester, N.Y., a corporation of New Jersey No Drawing. FiledMay 10, 1965, Ser. No. 454,698 9 Claims. (Cl. 260-488) ABSTRACT OF THEDISCLOSURE Novel compositions of matter which are 3,7,7-trialkylin whicheach of R, R and R is lower alkyl, and esters of such alcohols. Theinvention also includes specific processes for the preparation ofanalogous pyran derivatives. These alcohols, esters and pyranderivatives are useful as intermediates in the manufacture of perfumes.

This invention relates to a novel chamical process and, moreparticularly, to a novel process for the preparation of certain novel3,7,7-trialkyl--heptenols. The invention also relates to novelintermediates which are useful in the process of the invention andincludes the manufacture of certain valuable by-products which are alsoobtained in practicing the process of the invention.

In accordance with the process of the invention for preparing a3,7,7-trialkyl-5-heptenol, a 3,7,7-tn'alkyl-5- oxoheptanal is reduced.The reduction of the 3,7,7-trialkyl-S-oxoheptanal can be carried out byhydrogenation in the presence of a solid hydrogenation catalyst orchemically with a reducing agent, e.g., an alkali metal borohydride suchas sodium borohydride, an alkoxy-borohydride, an alkali metal hydride,etc. The reduction is preferably carried out catalytically as explainedmore fully hereinafter. The reaction product from the catalyticreduction of the 3,7,7-trialkyl-5-oxoheptanal contains either a2[2,2-dialkylethyl]-4alkyltetrahydropyran or a3,'7,7-trialkyl-5lhydroxyheptanol or a mixture thereof. The3,7,7-trialkyl-S-hydroxyheptanol is then esterified to form a diester of3,7,7-trialkyl-S-hydroxyheptanol and the diester is subjected topyrolysis under carefully controlled conditions to form a3,7,7-trialkyl-4-heptenol ester and a 3,7,7-trialkyl-5-heptenol ester.The 3,7,7-trialkyl-5- heptenol ester is then saponified to form a novel3,7,7- trialkyl-5-heptenol. Alternatively, the mixture of 3,7,7-trialkyl-4-heptenol ester and 3,7,7-trialkyl-5-heptenol ester 3,394,169Patented July 23, 1968 can be saponified to form a mixture of3,7,7-trialkyl-4- heptenol and 3,7,7-trialkyl-5-heptenol.

The 2[2,2-dialkylethyl]-4-alkyltetrahydropyran which is formed as aby-product in the process of the invention is a valuable compound, Ihave discovered these compounds can be produced by catalyticallyreducing the 3,7,7-trialkyl-5-oxoheptanal in the presence of a solidhydrogenation catalyst containing nickel or ruthenium.

I have discovered that maximum amounts of the 3,7,7-trialkyl-S-hydroxyheptanrol can be achieved if the 3,7,7-trialkyl-S-oxoheptanal is catalytically reduced in the presence of asolid hydrogenation catalyst containing copper.

The unusual selectivitiy of the hydrogenation reaction for the2[2,2-dialkylethyl]-4-alkyltetrahydropyran or for the3,7,7-trialkyl-S-hydroxyheptanol is completely unexpected. Thus, when anickel catalyst or a ruthenium on carbon catalyst is employed in thehydrogenation of the 3,7,7-trialkyl-S-oxoheptanal, the2[2,2-dialkylethyl] 4- alkyltetrahydropyran is obtained almost to theexclusion of other products whereas, when a copper catalyst is employed,the 3,7,7-trialkylS-hydroxyheptanol is obtained almost to the exclusionof other products. Other ruthenium catalysts, e.g., ruthenium oralumina, give a mixture of the two products.

I have also discovered that the 3,7,7-trialky1-5-hydroxyheptanol can beconverted to the 2[2,2-dialkylethyl1-4-alkyltetrahydropyran bycontacting the 3,7,7-trialkyl 5 hydroxyheptanol with an acidcyclodehydration catalyst. The acid cyclodehydration catalyst whicheffects the cyclodehydration of the 3,7,7 trialkyl 5 hydroxyheptanol canbe any of the acidic catalyst which have been employed in esterificationreactions. Useful acid cyclodehydration catalysts include mineral acid-ssuch as sulfuric acid, phosphoric acid, hydrochloric acid, nitric acid,etc., and aromatic sulfonic acids such as p-toluene sulfonic acid.Preferred as cyclodehydration catalysts are the aromatic sulfonic acids.

The cyclodehydration reaction, shown in Equation 5 of Table I below, iscarried out by contacting the 3,7,7- trialkyl-S-hydroxyheptanol with theacid cyclodehydration catalyst. The contacting is preferably carried outat elevated temperature, e.g., about C. to about 200 C. A preferredmethod for carrying out the contacting of the acid cyclodehydrationcatalyst and the 3,7,7-trialkyl-S-hydroxyheptanol is to heat a mixturecontaining the catalyst, the 3,7,7-trialkyl-S-hydroxyheptanol, and anorganic solvent which forms an azeotrope with water having a boilingpoint between about 50 C. and about 200 C. at its boiling point. Anexample of such an organic solvent is toluene. The water-tolueneazeotrope has a boiling point of about 84 C.

The process of my invention can be represented by the equations in Table1 below:

TABLE I 1] i... R CH CH2 0 OR R R O R In the preceding formulae in theequations in Table I for the process of the invention, each of thesubstituents R R and R is alkyl, preferably lower alkyl, and thesubstituent R is acyl, preferably alkanoyl. The substituents R R and Rare typical methyl, ethyl, propyl, isopropyl, butyl, sec-butyl,isobutyl, tert-butyl, etc. The substituent R is typically acetyl,propionyl, butyryl, isobutyryl, etc. Methyl is especially preferred asthe alkyl substituent represented by R R and R and acetyl is especiallypreferred as the acyl su'bstituent represented by R Examples of some ofthe 3,7,7-trialkyl-5-oxoheptanals which are useful in the process of theinvention are compounds such as 3,7-dirnethyl-5-oxooctana1;3,7-diethy1-5- oxononanal; 3,7-dipropyl-S-oxodecan-al; 3,7-clibutyl-5-oxoundecanal; 3,7-dipropyl-5-oxoundecanal; 3-methyl-7-propyl-S-oxodecanal; 3-rnethyl-7-ethyl-5-oxodecanal; etc.

Among the 2[2,2-dialkylethyl] 4- alkyltetrahydropyrans which can beprepared by the process of my invention are compounds such as2-isobutyl-4-methyltetrahydropyran;2[Z-methylbutyl]4-ethyltetrahydropyran; 2-[2- ethylhexyl]-4-isobutyltetrahydropyran; 2 2-butylhexyl 1 4-propyltetrahydropyran;etc. The novel 3,7,7-trialkyl-S-hydroxyheptanols of the invention areexemplified by compounds such as 3,7-dimethyl-S-hydroxyoctanol;3,7-dipropyl-5-hydroxydecanol; 3,7-diethyl-S-hydroxynonanol;3,7-dibutyl-5-hydroxyundecanol; 3-methyl-7-propyl-5-hydroxydecanol;3-methyl- 7-ethyl-5-hydroxydecanol; etc. The novel diesters of theinvention include diesters of the preceding 3,7,7-trialkyl-S-hydroxyheptanols with acids such as acetic acid, propionic acid,butyric acid, isobutyric acid, etc. Included among the novel3,7,7-trialkyl-5-heptenols and 3,7,7-trialkyl-S-heptenol esters of theinvention are alcohols such as 3,7-dimethyl-5-octenol;3,7-dipropyl-5-decenol; 3,7- diethyl-S-nonenol; 3,7-dibutyl-5-undecenol;3,7-diprpyl- S-undecenol; 3-methyl-7-propyl-5-decenol; 3-methyl-7-ethyI-S-decenol; etc., and esters thereof with acids such as aceticacid, propionic acid, butyric acid, isobutyric acid, etc.

The 3,7,7-tria1kyl-5-oxoheptan-als which are employed as the startingmaterials in the process of the invention can be prepared by contactinga 1,5,5-trialkyl-1-penten- 3-one, e.g., 6-methyl2-hepten-4-one, with analkyl vinyl ether, e.g., ethyl vinyl ether, and then contacting thereaction product with -a dilute aqueous solution of an acid, e.g.,phosporic acid. The preparation of 3,7,7-trialkyl-S-oxoheptanals by thisprocedure is described more fully in the copending application ofBrannock and Davis, Ser. No. 381,558, filed July 9, 1964 now U.S. PatentNo. 3,287,272.

The preferred 3,7,7-trialkyl--oxol1eptan-al for use in the process ofthe invention is 3,7-dimethyl-5-oxooctanal.

The reduction of the 3,7,7-trialkyl-S-oxoheptanal, shown in Equation 1of Table I, is preferably carried out by contacting the3,7,7-trialkyl-5-oxoheptanal with hydrogen at a temperature of about 75C. to about 200 C. and a pressure of about 500 to about 5,000 p.s.i. inthe presence of a solid hydrogenation catalyst. As indicatedhereinbefore, the preferred hydrogenation catalysts when a2[2,2-dialkylethyl]-4-alkyltetrahydropyran is desired are ruthenium oncarbon catalysts or nickel containing catalysts. These catalysts can besupported or unsupported. Thus, Raney nickel, nickel or rutheniumsupported on carbon, nickel on alumina, etc., are examples of suchpreferred catalysts. One such preferred nickel catalyst is nickelcatalyst G49A, available from the Girdler Co., Louisville, Ky.

When it is desired to maximize the yield of the 3,7,7-trialkyl-S-hydroxyheptanol, the preferred catalysts are those containingcopper. The preferred copper-containing catalysts for use in the processof the invention are those which also contain chromium. Examples of somepreferred copper and copper-chromium solid catalysts which are availablecommercially include those available from the Harshaw Chemical Co.,Cleveland, Ohio, under the designation Cu 2501-G4-10 and Cu 1407. Anespecially preferred copper-chromium catalyst is Copper ChromiteCatalyst 1106P of Harshaw Chemical Co. This catalyst contains 39 percentcupric oxide, 43 percent chromic trioxide, 10 percent barium oxide, and8 percent inert binder.

When the process of the invention is operated to produce a2[2,2dialkylethyl]-4-alkyltetrahydropyran, the reaction is preferablycarried out at a temperature of about C. to 200 C. and a pressure offrom about 500 to about 5,000 p.s.i. Especially preferred reactionconditions when operating the process of the invention to produce amaximum amount of 2[2,2-dialkylethyl]-4-alkyltetrahydropyran include atemperature of from about C. to about C. and a pressure of from about1,500 to about 2,500 p.s.i. When using a copper-containing catalyst toproduce a maximum amount of a 3,7,7-tr-ialkyl-S-hydroxyheptanol, theprocess of the invention is preferably carried out at a temperature offrom about 100 C. to about 200 C. and a pressure of from about 1,000 toabout 5,000 p.s.i. Especially preferred operating conditions forproducing a, maximum amount of 3,7,7-trialkyl-S-hydroxyheptanol includea temperature of from about 125 C. to about C. and a pressure of fromabout 2,000 to about 3,000 p.s.i.

The 3,7,7-trialkyl-5-hydroxyheptanol diesters which are pyrolyzed in theprocess of the invention can be prepared as shown in Equation 2 of TableI by conventional means by reacting an organic carboxylic acid or anorganic carboxylic acid anhydride with a3,7,7-trialkyl-5-hydroxyheptanol. The preferred diesters for use in theprocess of the invention are diesters formed from a3,7,7-trialkyl-5-hydroxyheptanol and a lower alkanoic acid such asacetic acid, propionic acid, butyric acid, etc.

The pyrolysis of the 3,7,7-trialky1-5-hydroxyheptanol diester inaccordance with Equation 3 of Table I must be carried out undercarefully controlled conditions. Thus the reaction temperature must bemaintained between about 350 C. and about 425 C. The reactiontemperature is preferably controlled between about 360 C. and 390 C. Thepyrolysis of the 3,7,7-trialkyl-5-hydroxyheptanol diester can be carriedout by passing the diester through a reaction zone which is maintainedat the desired temperature. The reaction zone can contain inert packingto aid in maintaining the desired temperature throughout the reactionzone. In some instances it is preferred to dilute the diester with aninert volatile solvent before the diester is passed through the reactionzone. Benzene is a suitable organic solvent for use as such a diluent.

The efiluent from the reaction zone contains a 3,7,7-trialkyl-4-heptanol ester and a 3,7,7,-trialkyl-5-heptanol ester. Thealcohols, i.e., 3,7,7,-trialkyl-4-heptanol and the3,7,7,-trlalkyl-5-heptanol, are obtained by saponifying the esters whichare produced in the pyrolysis reaction as shown in Equation 4 of TableI. The saponification of the 3,7,7-trialkyl-4-heptanol ester and the3,7,7-trialkyl- 5-heptanol ester can be carried out by conventionalmeans. Thus the mixture of esters can be saponified by warming them inthe presence of water with a small amount of sodium hydroxide or otheralkali metal hydroxide.

The following examples illustrate the preparation of a3,7,7-trialkyl-S-heptanol in accordance with the process of myinvention.

EXAMPLE 1 Ethanol (70 ml.), 3,7-dimethyl-5-oxooctanal (70 g., 0.41 mole)and a copper chromite catalyst (Harshaw 1106-?) were heated in anautoclave at 150 C. and 2,500 p.s.i. hydrogen pressure until no furtherhydrogen was absorbed. The catalyst was removed and the3,7-dimethyl-1,5-octanediol (53 g.) distilled. RP. 124'125 C./1.5 mm.,11 1.4558.

Analysis.Calcd.: C, 69.0%; H, 12.7%. Found: C, 69.02%; H, 12.77%.

EXAMPLE 2 The diacetate of the 3,7-dimethyl-1,5-octanediol (34 g, 0.13mole) of Example 1 was diluted with an equal volume of benzene andpassed through a Vycor tube 1 in. x 12 in. packed with Vycor chips andheated to 370 C. with an electric furnace. The addition rate wasapproximately 1 ml./min. The elfiuent, by gas chromatography, was amixture of acetic acid, benzene, 3,7-dimethyl-4-octenyl acetate and3,7-dimethyl-5-octenyl acetate. The 3,7-dimethyl-4-octenyl acetate andthe 3,7-dimethyl-5-octenyl acetate were distilled at 5 8 C./ 0.5 mm.Weight 17 g., n 1.4368. NMR and infrared data agreed with the proposedstructure. By gas chromatography the product was approximately a 50-50mixture of the 3,7- dimethyl-4-octenyl acetate and3,7-dimethyl-5-octenyl acetate. On saponification a mixture of thecorresponding unsaturated alcohols was obtained. B.'P. 77.78 C./ 2 mm.,n 1.4479. These alcohols have an odor very similar to that ofcitronellol, an important article of commerce The following examplesillustrate the preparation of a2[2,2-dialkyethyl]-4-alkyltetrahydropyran according to the process ofthe invention.

EXAMPLE 3 EXAMPLE 4 Example 3 was repeated except that ruthenium onalumina was used as a catalyst. The product was a mixture of2-isobutyl-4-methyltetrahydropyran and 3,7-dimethyl-1,5-octanediol in aratio of about 1 to 2. Infrared and other data indicated the compoundswere identical to the compounds of Examples 3 and 1, re spectively.

EXAMPLE 5 Toluene (100 ml.), 3,7'dimethyl-1,5-octanediol (17.4

g., 0.1 mole) and p-toluene sulfonic acid (0.05 g.) were refluxed undera Dean-Stark trap until 1.8 ml. of water had been removed. The solutionwas washed with water until neutral and the toluene was removed bydistillation. The 2-isobutyl-4-methyltetrahydropyran (10 g.) wasdistilled at 41 C./1 rnm., 11 1.4350. Infrared data was in agreementwith that of Example 3. By gas chromatography the two samples wereidentical except that this sample contained more of the trans isomerthan that of Example 1.

The products and byproducts of the process of the invention are usefulin the perfume industry. Thus 2- isob-utyl-4-rnethyltetrahydropyran, aprefered 2[2,2-dialkylethyl]-4-alkyltetrahydropyran, which is producedas a by-product in the hydrogenatio nof 3,7-dimethyl-5-oxooctanal, iscommonly called dihydro rose oxide and is disclosed in Bull. Soc. Chim.,France, 1961, 645-57. This compound, which has a pleasant odor, isuseful in the formulation of perfumes or in perfumed soaps and toiletarticles. The compound 3,7-dimethyl-5-octcn-1-01, a preferred3,7,7-trialky1-5-heptenol, produced in the process of our invention, hasa pleasant odor somewhat similar to citronellol and is useful in theperfume and flavoring industries as a substitute for citronellol.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention as described hereinbefore and as defined in theappended claims.

I claim:

1. An ester of the formula:

R R Il )HOH=CH-CH HCH;z-CHz-OR in which each of R R and R is lower alkyland R is lower alkanoyl.

2. A lower alkanoic acid ester of 3,7-dimethyl-5-octenol.

3. 3,7-dimethyl-5-octenyl acetate.

4. An alcohol of the formula:

R R IL 3H-GH=CH-CH2-(9HCHzCHr-OH in which each of R R and R is loweralkyl.

5. 3,7-dimethyl-5-octenol.

6. A compound of the formula:

R OH R R (9HCHz'-(9HCH2( 3 11- C HIE-C Ha-O H in which each of R R and Ris lower alkyl.

7. A compound of the formula:

8. 3,7-dimethyl-S-hydroxyoctanol.

9. A lower alkanoic acid \diester of 3,7-dimethyl-5-hy droxyoctanol.

References Cited UNITED STATES PATENTS 2,768,978 10/1956 Robertson260-345.1 XR 2,843,607 7/1958 Seryigne et al. 260-494 XR 3,004,3119/1962 Milligan 260345.l XR 3,052,730 9/1962 Eschinazi 260-638 XR3,077,495 2/ 1963 Levine 260-494 XR 3,147,267 9/1964 Rogers 260-345.1 XR3,166,575 l/1965 Naves 260--345.1

HENRY 1R. JILES, Primary Examiner.

J. M. FORD, Assistant Examiner.

